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World Rural Observations 2010, 2(2) http://www.sciencepub.net/rural Regional groundwater flow modeling in Western Nile Delta, Egypt Rani Fouad Mohamed (1), (2), Chen Zhi Hua (1) (1) School of Environmental Studies, China University of Geosciences, 388 Lumo Road, Wuchang,Wuhan, Hubei, P.R.China; Zip code: 430074. (2) Faculty of Engineering, Alazhar University, Nasr city, Cairo, Egypt; Zip code: 11341 [email protected]; Tel: 00862762626996 Abstract: Western Nile delta is an important area in Egypt in which the government plans to establish new reclamation projects. The already present agricultural activities are mainly based on groundwater for irrigation. However, irrigation requirements have become so large that they cause depletion of the groundwater levels in most of the existed wells. A hydrogeological model for western Nile delta has been developed using MODFLOW code. The developed model was calibrated for steady state, and used to evaluate groundwater potentiality and reserves. The results have shown that; a reduction in groundwater abstraction by at least 20% becomes necessary to achieve sustainable conditions. This study can be considered as a preliminary regional evaluation for testing the future alternative water management scenarios in Western Nile Delta area. [Rani Fouad Mohamed, Chen Zhi Hua. Regional groundwater flow modeling in Western Nile Delta, Egypt. World Rural Observations 2010;2(2):37-42]; ISSN: 1944-6543 (Print); ISSN: 1944-6551 (Online). http://www.sciencepub.net/rural. Keywords: Groundwater modeling, Groundwater/surface-water interaction, western Nile delta. Introduction the Qattara Depression, the study area covers about Groundwater is an important source for water 15170.6 km2 as shown in Figure [1]. supply in Egypt, Nile water alone is no longer sufficient for the increasing water requirements for Hydrogeological setting different development activities. However, many Western Nile Delta region distinguished into cautions and worries are increasingly being voiced on three aquifers, Quaternary aquifer, Pliocene aquifer and the dangers that surround the groundwater resources. the Moghra aquifer. The main aquifer in the Nile Delta The main elements of these worries are related to is the Quaternary aquifer. The saturated thickness of depletion as a result of over abstraction. Western Nile Quaternary aquifer ranges between 50 m along the delta has limited water resources although it lies on the desert fringes in the West to 800 m in the North while western part of Nile Delta aquifer. The government it reaches about 200 m in the South near El Kanter El established canals network to divert surface water to Khiria City. The aquifer is semi-confined in the Delta area, this area but farmer still suffering from shortage of being overlain by a Holocene layer of sandy clay and silt, surface water and use the groundwater wells. There are and in the area of Nubaria, where aquifer is covered by more wells operating within the basin. Due to excess loamy deposits. In the rest of the area, the aquifer is abstraction from these public and private wells (1.90 phreatic (unconfined). The Moghra aquifer is the main BCM), the water level in the well fields declined aquifer in the southern and western portions of the study significantly. Water table’s decrease leads to salt-water area. The aquifer is overlain by Pliocene and underlain by intrusion with the Mediterranean Sea. The farms Oligocene basalt or shales. Both aquifers are connected become covered with the saline water RIGW/IWACO with each other in a direct hydraulic contact along the (1998). To avoid the deterioration of the aquifer system stretch Khatatba-Abu Rawash (lateral) and along the in this area an efficient integrated and sustainable stretch Sadat City-Khatatba (vertical). While in all other management plan for groundwater resources is needed. locations, the two-aquifer systems are separated by Groundwater modeling is the best tool to predict the Pliocene deposits. response of the groundwater aquifer and estimate the The piezometric head level of groundwater is safe yield (Xuesen Mao et al., 2005). generally decreasing within the Western Nile Delta from more than 15 m +MSL in Cairo to 1 m +MSL Study area near the coast. The piezometric level decreases from Western Nile Delta region occupies the area south to north by an average piezometric gradient about between Cairo at equator and Alexandria, west of 0.00011. The groundwater levels are usually oscillating Rosetta branch, and extends westward to the desert area up and down affected by one or more of the following, from the west of Wadi el-Natrun up to the eastern edge of levels of water in the river Nile and its distributors, method and frequency of irrigation, horizontal and 37 World Rural Observations 2010, 2(2) http://www.sciencepub.net/rural vertical agricultural extensions, and groundwater extraction by wells are the main discharge components extraction. from the aquifer. In 1985 the annual abstraction for Recharge to the aquifer takes place due to three both drinking water and irrigation was 460 million factors Infiltration, Infiltration and downward leakage cubic meters and increased to 635 million cubic meters of excess surface irrigation water (originating from the in 1997. Due to increase in desert fringes reclamation River Nile) and, Leakage from canals. in the Western Nile Delta region in the end of nineties, Discharge of groundwater takes place through the abstraction from groundwater increased four processes: outflow into the drainage system, direct dramatically to 1370 million cubic meters. The recent abstraction, evapotranspiration and inter-aquifer flow filed investigations estimate current abstraction as 1.9 of groundwater. Groundwater return flow to the river BCM. Nile and drains (open drains and tile drains) as well as 29 30 30 00 30 30 Lake Burulus 31 00 Rashid Mediterranean Sea (Rosetta) Abo QIR Edko El Monatazah Alexandria ( Kafr R El Mahmudya o Selim s N Kaffr El Dauwar et i El Dekhila ta le North Abu Hummus b r an Damanhur c Shubra Khit h) Behira 31 00 Hosh Isa Burg El Arab Abo El Matamir Itay El Barod El Delingat Kom Hamada Mudiriyat Eltahrir Talet Elgarw Mudiriyet el Tahrir Gabel Naum Liberation Provience W a di El N a El Khatatba 30 30 tr un Sadat City Banha Gabel Hadid Khasm Elkalb Gabel Qentara Legend Wadi El Farigh Gabel Rozza Gabel Gubr Giza Cairo Main Roads 6th of October City Railway Sutdy Area Scale 1 : 1.000.000 30 0029 30 30 0029 30 30 31 00 Figure [1], Western Nile Delta Location Model development Model set-up To develop the numerical simulation for the aquifer system MODFLOW code has been selected to simulate three dimensional steady state groundwater flows for the study area. The model consists of multi-layers aquifer system. The first layer represents the semi-confining layer (upper clay layer), which overlies the main aquifer. It is modeled as an aquifer in which vertical and horizontal flows simulated. A finite difference grid is generated for the modeled area. The grid consists of 100 rows and 100 columns, for a total of 10 000 cells. All of the cells have uniform dimensions of 1.6 km by 1.6 km; the cell size is small enough to reflect both the density of input data and the desired output detail, and large enough for the model to be manageable. All surface water features such as the river, main irrigation canals and main open drains are simulated as ‘rivers’ in the model. The exchange between those ‘rivers’ and the aquifer systems is calculated with Darcy’s equation, and expressed as follows: K q v D= H [1] b Equation (1) can be rewritten in the following form: 38 World Rural Observations 2010, 2(2) http://www.sciencepub.net/rural )H - H ( C Q = C ( H - aquiferriverrch )H [2] K and C = v [3] b where q is the flow between the river and the aquifer (positive for baseflow - for gaining streams and negative for river recharge – for losing streams); C is a constant representing the streambed leakage coefficient K (hydraulic conductivity of semi-impervious streambed stratum v divided by its thickness b); and DH is the difference between the water level in the river H river and the groundwater level in aquifer H aquifer . Boundary conditions The aquifer boundaries can be described by two types of hydrological conditions. No flow boundary is applied for the southern boundary where a fault exists and previous studies showed that no flow can be from the western desert enters the aquifer system (Mohamed A. et al., 2005). Constant head boundary is used for the eastern, northern and western boundaries; the constant head data were obtained from hydrogeologic map for the Nile delta, as shown in Figure [2]. 971502 Mediterranean Sea Alexandria (R o s N et i ta le West Nile Delta b ra n Damanhur ch North 930000 ) Tanta 900000 870000 North Western Desert 840000 Legend Cairo Contour line Scale 1 : 1.000.000 809492 470586 540000 570000 600000 638475510000 Figure [2], Constant head in Western Nile Delta Model calibration model development. The only parameters contributing The numerical model was calibrated under to the uncertainty of the model simulations were: (a) steady-state conditions through a series of groundwater the hydraulic conductivity, and (b) the distribution of flow simulations. The conceptualization of the regional the areal recharge rate. Fig. [1] Shows the initial flow and the relatively complex model architecture hydraulic conductivity distribution for the aquifer were precisely defined in the preliminary stage of the system. During the calibration, the simulated recharge 39 World Rural Observations 2010, 2(2) http://www.sciencepub.net/rural distribution was depend on the following values, In the average; the simulated water level differs by about 30 central and southern portions of the flood plain, the cm from the observed water level.